21504025 has 24 divisors (see below), whose sum is σ = 27676800. Its totient is φ = 16564800.

The previous prime is 21504023. The next prime is 21504047. The reversal of 21504025 is 52040512.

It is not a de Polignac number, because 21504025 - 2¹ = 21504023 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21503993 and 21504011.

It is not an unprimeable number, because it can be changed into a prime (21504023) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 89856 + ... + 90094.

It is an arithmetic number, because the mean of its divisors is an integer number (1153200).

Almost surely, 2^21504025 is an apocalyptic number.

21504025 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21504025 is a deficient number, since it is larger than the sum of its proper divisors (6172775).

21504025 is a wasteful number, since it uses less digits than its factorization.

21504025 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 369 (or 364 counting only the distinct ones).

The product of its (nonzero) digits is 400, while the sum is 19.

The square root of 21504025 is about 4637.2432543484. The cubic root of 21504025 is about 278.0822393546.

Adding to 21504025 its reverse (52040512), we get a palindrome (73544537).

The spelling of 21504025 in words is "twenty-one million, five hundred four thousand, twenty-five".